Diabetes is a life-style related disease and the number of patients increases all over the world. The treatments for diabetes are classified into diet, exercise and drug therapy (injectable insulin and an oral anti-diabetic drug). Some oral anti-diabetic drugs, for example, α-glucosidase inhibitors (acarbose, voglibose), insulin-sensitizing agents (pioglitazone hydrochloride), biguanides (metformin hydrochloride), sulfonylureas (glibenclamide, glimepiride) and short-acting insulin secretagogues (mitiglinide calcium hydrate) are commercially available in Japan.
On the other hand, an incretin mimetics (excenatide) and a DPP IV inhibitor (sitagliptin), which accelerates secretion of insulin, are commercially available abroad. The incretin is a gastrointestinal hormone, which accelerates secretion of insulin. Further, SGLT inhibitors have been developed abroad.
GPR119 has been reported as a G protein-coupled-receptor (GPCR) whose endogenous ligand is N-oleoylethanolamide and which stimulate insulin secretion from pancreatic β-cells (Non-patent Document 1: Overton H A at al., Cell Metab., 2006, 3, 167-75). It has been reported that GPR119 agonist increases the plasma concentration of Glucagon like peptide-1 (GLP-1), one of incretins (Non-patent Document 2: Chu Z L at al., Endocrinology, 2008, 149, 2038-47), which may indirectly relate to stimulation of insulin secretion. It has been further reported that GPR119 agonist surpresses a weight increase in rats fed a high-fat diet (Non-patent Document 1), which may relate to energy metabolism. For the reasons mentioned above, the GPR119 agonist has been expected as a drug not only for diabetes but also for life-style related diseases such as obesity and metabolic syndrome.
Compounds such as (A) are described in WO 2004/076413 (Patent Document 1) as the GPR119 agonist.

Compounds such as (B) are described in WO 2004/065380 (Patent Document 2) as the GPR119 agonist.

Compounds such as (C) are described in WO 2005/007647 (Patent Document 3) as the GPR119 agonist.

Compounds such as (D) are described in WO 2007/003960 (Patent Document 4) as the GPR119 agonist.

Compounds such as (E) are described in WO 2008/025798 (Patent Document 5) as the GPR119 agonist.

Compounds such as (F) are described in WO 2008/008887 (Patent Document 6) as the GPR119 agonist.

However, there in no description of the compound represented by the formula (I) in which the carbon atom contained in the pyridine or pyridazine ring is directly combined with the carbon atom contained in the cyclic amine.
Compounds such as (G) and (H) are described in WO 97/09311 (Patent Document 7), which have a pyridylpiperidine structure.

Compounds such as (J) are described in WO 2002/042305 (Patent Document 8).

These compounds are intermediates of a drug for Alzheimer disease or GABAA agonist. There is no description in Patent Documents 7 and 8 that these compounds are used as GPR119 agonists.